The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to embodiments of the claimed subject matter.
In the communications arts there is a phenomenon known as the “near-far problem” in which receivers capturing strong signals have difficulty simultaneously detecting weaker signals. In the DSL arts specifically, an upstream near-far problem may exist in which crosstalk from near-end (strong) users impacts signaling of far-end (weak) users, or in which users coupled with short loops exhibit stronger signals than users on longer more attenuated loops, and thus, the stronger signaling users significantly degrade the weaker signaling users' data rates.
DSL transmissions are negatively impacted by crosstalk and such effects are exhibited most strongly with short loops. Moreover, such crosstalk is especially problematic for transmissions in the upstream direction where DSL upstream transmissions on short loops cause very strong crosstalk to DSL upstream transmissions on longer loops, thus resulting in the well known near-far problem.
In a laboratory setting it may be feasible to architect an experiment with DSL lines or loops of approximately equal length such that across the board power control parameters would suffice. Optionally, vectoring could be applied to all of the lines so as to perfectly cancel all crosstalk. However, it is very well understood by those skilled in the relevant arts that such pristine laboratory conditions simply do not translate to the real world. Actual DSL deployments in the field commonly consist of both shorter and longer DSL loops as well as potentially non-vectored lines co-located with DSL loops of a vectored group.
Instituting what is known as a power back-off for all lines is a simple solution to reduce crosstalk but also results in lower transmission rates and is therefore impractical for many deployments. Vectoring as noted above greatly reduces crosstalk but requires new equipment to be deployed and thus may not be available or may only be available on a sub-set of co-located DSL lines, and thus does not solve the problem of crosstalk for those non-vectored lines or for vectored lines which operate near non-vectored lines.
The present state of the art may therefore benefit from methods, systems, and apparatuses for implementing upstream power control for DSL as described herein.